Variable Pitch Fan Control System

ABSTRACT

A fan control system for a variable pitch fan of a work vehicle includes a first sensor that measures a parameter of a cooling system and a blade pitch module that adjust a pitch of a plurality of blades of the variable pitch fan to generate airflow in a first direction. A reversing module selectively commands a fan reversal that includes instructing the blade pitch module to temporarily adjust the pitch of the plurality of blades to generate airflow in a second direction. A first timer module, in response to the reversing module commanding the fan reversal, resets and increments a first timer and compares the first timer to a first threshold. A first reversal prevention module, in response to the first timer being less than the first threshold, prevents the reversing module from commanding a fan reversal by indicating that a first type of fan reversal is not permitted.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Indian Patent Application No.202021022332, filed May 28, 2020. The entire disclosure of theapplication referenced above is incorporated by reference.

FIELD

The present disclosure relates to the control of a fan in a workvehicle, and more particularly to the control of a variable pitch fan ina work vehicle.

BACKGROUND

Work machines, such as those in the agricultural, construction, andforestry industries, may include a cooling system for providing air flowto an engine or other heat-generating device of the work machine. Heatexchangers (e.g., air coolers), fans, and the like may form part of thecooling system. During a work operation, debris and other particulatescan enter the cooling system and cause problems with cooling theengine—for example, clogging an air inlet of a heat exchanger or fan. Itis often necessary to perform a cleaning operation to remove the debrisfrom the cooling system. To do so, however, can be difficult as debriscan often reach areas in the cooling system that are difficult to reachwithout removing or moving components such as a heat exchanger or fan toaccess those areas.

The background description provided here is for the purpose of generallypresenting the context of the disclosure. Work of the presently namedinventors, to the extent it is described in this background section, aswell as aspects of the description that may not otherwise qualify asprior art at the time of filing, are neither expressly nor impliedlyadmitted as prior art against the present disclosure.

SUMMARY

A fan control system for a variable pitch fan of a work vehicle includesa first sensor configured to measure a parameter of a cooling system ofthe work vehicle and a blade pitch module configured to receive themeasured parameter from the first sensor and adjust a pitch of aplurality of blades of the variable pitch fan based on the measuredparameter to generate a first airflow in a first direction. The systemalso includes a reversing module configured to selectively command a fanreversal that includes instructing the blade pitch module to temporarilyadjust the pitch of the plurality of blades of the variable pitch fan togenerate a second airflow in a second direction. The second direction isopposite to the first direction. The system further includes a firsttimer module configured to reset and increment, in response to thereversing module commanding the fan reversal, a first timer and comparethe first timer to a first threshold. The system also includes firstreversal prevention module configured to, in response to determiningthat the first timer is less than the first threshold, prevent thereversing module from commanding a fan reversal by indicating that afirst type of fan reversal is not permitted.

In other features, the fan control system includes a second sensor thatmonitors a status of a clutch of the work vehicle and a second timermodule configured to (i) receive the status of the clutch from thesecond sensor, (ii) in response to the status of the clutch indicatingthat the clutch is engaged, increment a second timer, and (iii) comparethe second timer to a second threshold. The reversing module isconfigured to command a fan reversal in response to determining that (i)the second timer is equal to or greater than the second threshold and(ii) the first reversal prevention module does not indicate that thefirst type of fan reversal is not permitted.

In yet other features, the fan control system includes a second reversalprevention module configured to, in response to determining that thefirst timer is less than the first threshold, prevent the reversingmodule from commanding the fan reversal by indicating that a second typeof fan reversal is not permitted. The reversing module is configured toreceive an instruction, via an operator interface, that requests thesecond type of fan reversal and command the fan reversal in response to(i) receiving the instruction and (ii) determining that the secondreversal prevention module does not indicate that the second type of fanreversal is not permitted.

In other features, the work vehicle includes an engine. The fan controlsystem further includes a second sensor configured to measure a speed ofthe engine and an engine state module configured to (i) receive themeasured engine speed from the second sensor, (ii) compare the measuredengine speed to a first speed threshold, and (iii) compare the measuredengine speed to a second speed threshold. The first reversal preventionmodule is configured to, in response to determining that (i) themeasured engine speed is less than the first speed threshold or (ii) themeasured engine speed is greater than the second speed threshold,indicate that the first type of fan reversal is not permitted. The firstspeed threshold is less than the second speed threshold.

In further features, the engine state module is configured to comparethe measured engine speed to a third speed threshold. The fan controlsystem further includes a second reversal prevention module configuredto, in response to determining that (i) the engine speed is less thanthe third speed threshold or (ii) the engine speed is greater than thefirst threshold, prevent the reversing module from commanding a fanreversal by indicating that a second type of fan reversal is notpermitted. The reversing module is configured to receive an instruction,via an operator interface, that requests the second type of fanreversal, and command the fan reversal in response to (i) receiving theinstruction and (ii) determining that the second reversal preventionmodule does not indicate that the second type of fan reversal is notpermitted. The third speed threshold is less than both the first speedthreshold and the second speed threshold.

In other features, the fan control system includes a third sensor thatmeasures an ambient temperature associated with the work vehicle. Thefirst reversal prevention module is configured to receive the measuredambient temperature from the third sensor, and in response todetermining that the received ambient temperature is less than atemperature threshold, indicate that the first type of fan reversal isnot permitted.

In other features, the fan control system includes a cooling systemmodule configured to set a state of the cooling system based on faultcodes associated with one or more components of the cooling system, andin response to receiving at least one fault code, set the state of thecooling system to an error state. The first reversal prevention moduleis configured to, in response to determining that the cooling system isin an error state, indicate that the first type of fan reversal is notpermitted.

A method for controlling a variable pitch fan of a work vehicle, themethod includes measuring a parameter of a cooling system of the workvehicle, performing a first fan reversal including temporarily adjustingthe pitch of the plurality of blades of the variable pitch fan togenerate a second airflow in a second direction, and resetting andincrementing a first timer in response to performing the fan reversal.The method further includes comparing the first timer to a firstthreshold and preventing a second fan reversal, in response todetermining that the first timer is less than the first threshold.

In other features, the method includes receiving, from a second sensor,a status of a clutch of the work vehicle, resetting a second timer inresponse to performing the first fan reversal, and incrementing thesecond timer in response the status of the clutch indicating that theclutch is engaged. The method also includes comparing the second timerto a second threshold and performing a second fan reversal in responseto determining that the first timer is greater than the first thresholdand the second timer is greater than the second threshold.

In other features, the method includes performing a second fan reversalin response to (i) receiving a reversal request from an operator of thework vehicle and (ii) determining that the first timer is greater thanthe first threshold.

In other features, the work vehicle includes an engine. The methodincludes measuring a speed of the engine, comparing the measured enginespeed to a first speed threshold, and comparing the measured enginespeed to a second speed threshold. The method also includes performing asecond fan reversal in response to determining that (i) the first timeris greater than the first threshold, (ii) the measured engine speed isgreater than the first speed threshold, and (iii) the measured enginespeed is less than the second speed threshold. The first speed thresholdis less than the second speed threshold.

In further features, the method includes comparing the measured enginespeed to a third speed threshold and performing a second fan reversal inresponse to receiving a reversal request from an operator of the workvehicle and determining that (i) the first timer is greater than thefirst threshold, (ii) the measured engine speed is greater than thethird speed threshold, and (iii) the measured engine speed is less thanthe second speed threshold. The third speed threshold is less than boththe first speed threshold and the second speed threshold.

In other features, the method includes receiving, from a third sensor,an ambient temperature associated with the work vehicle, comparing thereceived ambient temperature to a temperature threshold, and performinga second fan reversal in response to determining that the first timer isgreater than the first threshold and the received ambient temperature isgreater than the temperature threshold.

In other features, the method includes determining, in response toreceiving a fault code associated with a component of the coolingsystem, that the cooling system is in an error state. The method furtherincludes performing a second fan reversal in response to the determiningthat (i) the first timer is greater than the first threshold, (ii) thesecond timer is greater than the second threshold, and (iii) the coolingstate is not in an error state.

A non-transitory computer-readable medium storing processor executableinstructions for controlling a variable pitch fan of a work vehicle, theinstructions includes measuring a parameter of a cooling system of thework vehicle, adjusting a pitch of a plurality of blades of the variablepitch fan based on the parameter to generate a first airflow in a firstdirection, and performing a first fan reversal including temporarilyadjusting the pitch of the plurality of blades of the variable pitch fanto generate a second airflow in a second direction. The instructionsfurther include resetting and incrementing a first timer in response toperforming the fan reversal, comparing the first timer to a firstthreshold, and preventing a second fan reversal, in response todetermining that the first timer is less than the first threshold.

In other features, the instructions include receiving, from a secondsensor, a status of a clutch of the work vehicle, resetting a secondtimer in response to performing the first fan reversal, and incrementingthe second timer in response the status of the clutch indicating thatthe clutch is engaged. The instructions further include comparing thesecond timer to a second threshold and performing a second fan reversalin response to determining that the first timer is greater than thefirst threshold and the second timer is greater than the secondthreshold.

In other features, the instructions include performing a second fanreversal in response to (i) receiving a reversal request from anoperator of the work vehicle and (ii) determining that the first timeris greater than the first threshold.

In other features, the work vehicle includes an engine. The instructionsinclude measuring a speed of the engine, comparing the measured enginespeed to a first speed threshold, and comparing the measured enginespeed to a second speed threshold. The instructions further includeperforming a second fan reversal in response to determining that (i) thefirst timer is greater than the first threshold, (ii) the measuredengine speed is greater than the first speed threshold, and (iii) themeasured engine speed is less than the second speed threshold. The firstspeed threshold is less than the second speed threshold.

In yet further features, the instructions include comparing the measuredengine speed to a third speed threshold and performing a second fanreversal in response to receiving a reversal request from an operator ofthe work vehicle and determining that (i) the first timer is greaterthan the first threshold, (ii) the measured engine speed is greater thanthe third speed threshold, and (iii) the measured engine speed is lessthan the second speed threshold. The third speed threshold is less thanboth the first speed threshold and the second speed threshold.

In yet other features, the instructions include determining, in responseto receiving a fault code associated with a component of the coolingsystem, that the cooling system is in an error state. The instructionsalso include performing a second fan reversal in response to thedetermining that (i) the first timer is greater than the firstthreshold, (ii) the second timer is greater than the second threshold,and (iii) the cooling state is not in an error state.

Further areas of applicability of the present disclosure will becomeapparent from the detailed description, the claims, and the drawings.The detailed description and specific examples are intended for purposesof illustration only and are not intended to limit the scope of thedisclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will become more fully understood from thedetailed description and the accompanying drawings.

FIG. 1 is a perspective view of an example work vehicle including a fancontrol system according to the principles of the present disclosure.

FIG. 2 is a side view of an example work vehicle including a fan controlsystem according to the principles of the present disclosure.

FIG. 3 is a partial view of an example variable pitch fan.

FIG. 4 is a functional block diagram of an example implementation of afan control system according to the principles of the presentdisclosure.

FIGS. 5A-5C are a flowchart of example operations performed by animplementation of the fan control system.

In the drawings, reference numbers may be reused to identify similarand/or identical elements.

DETAILED DESCRIPTION

FIGS. 1 and 2 illustrate an example work vehicle 10. The illustratedwork vehicle 10 is a cotton harvester 15—for example, a cotton picker ora cotton stripper. Although the work vehicle 10 is depicted as a cottonstripper and a cotton picker, other types of work vehicles—for example,combine harvesters, tractors, self-propelled sprayers, and other typesof off-road work machines—are contemplated by this disclosure.

The work vehicle 10 includes a chassis 20. The illustrated chassis 20 issupported by front ground engaging members 25 and rear ground engagingmembers 30. Although the front ground engaging members 25 and rearground engaging members 30 of the work vehicle 10 are depicted aswheels, other supports are contemplated—for example, tracks. The workvehicle 10 is adapted for movement through a field 35 to perform a task,such as harvesting crops. As examples only, work vehicle 10 may beconfigured to harvest cotton, corn, soybeans, canola, stover, hay,alfalfa, or other agricultural crops. An operator station 40 issupported by the chassis 20.

An operator interface 45 is positioned in the operator station 40. Insome implementations, the operator interface 45 includes a displayscreen—for example, a liquid crystal display (LCD), a light emittingdiode (LED) screen, an organic LED (OLED) screen, or a CRT display. Thedisplay screen of the operator interface 45 may present, via a graphicaluser interface (GUI), various features and/or parameters of the workvehicle 10. In various implementations, the operator interface 45 mayinclude one or more user input devices—for example, buttons, switches,touch screens, and/or levers. The operator of the work vehicle 10 mayadjust various operating parameters of the work vehicle 10 via theoperator interface 45—for example, by actuating one or more of the userinput devices.

Referring to FIG. 2, a power module 50 may be supported below thechassis 20. The power module may be an engine 55 that drives a hydraulicmotor 60 or a mechanical drive 65 to power a variable pitch fan 70. Anoperator may set a minimum power for the power module 50 from theoperator interface 45. The operator may also set a minimum engine speedfrom the operator interface 45. Water, lubricant, and fuel tanks,indicated generally at 75, may be supported on the chassis 20.

The work vehicle 10 may include a compressor (not shown)—for example, aturbocharger—that compresses air into a combustion chamber of the engine55 to increase the engine's combustion efficiency and/or power output.During the air compressing process in the compressor, the temperature ofthe air increases. A charge air cooler—for example, a heat exchanger—maybe coupled between the compressor and the engine 55 to reduce thetemperature of the air, referred to as charge air temperature, after theair passes through the compressor but before the air enters the engine55.

A harvesting structure 80 is coupleable to the chassis 20. Theillustrated harvesting structure 80 is configured to remove cotton fromthe field 35. The harvesting structure 80 may be a cotton stripperheader 85 (FIG. 1), one or more cotton picking units 90 (FIG. 2), oranother harvesting structure. Alternatively, the harvesting structure 80may be configured to remove corn or another crop—for example, theharvesting structure 80 may a corn header or a draper header (notshown).

With reference to FIGS. 1 and 2, an air duct system 95 is coupleable tothe harvesting structure 80. A crop receptacle 100 is coupleable to theair duct system 95. Referring to FIG. 1, the illustrated crop receptacle100 is a round module builder 105. Alternatively, the crop receptacle100 may be a basket (not shown). The illustrated round module builder105 includes a cleaner 108 that cleans the cotton harvested from thecotton stripper header 85 by removing trash and debris. With referenceto FIG. 2, the round module builder 105 includes an accumulator 110 thatis configured to receive cotton, or other crop, harvested by thecotton-picking units 90.

With continued reference to FIG. 2, a feeder 115 is coupleable to thechassis 20. The feeder 115 is configured to receive cotton, or othercrop, from the accumulator 110. The feeder 115 includes a plurality ofrollers 120 configured to compress the cotton, or other crop, andtransfer the cotton, or other crop, to a baler 125 of the round modulebuilder 105.

As shown in FIG. 2, the work vehicle 10 includes a clutch sensor 150, aground speed sensor 152, an ambient sensor 155, an engine speed sensor160, cooling system sensors 162, and a fan control module 165. Theclutch sensor 150 monitors the state of a clutch (not shown) of the workvehicle 10—for example, a separator clutch or a cotton fan clutch. Theoutput of the clutch sensor 150 may indicate that the clutch is eitherengaged or disengaged. The ground speed sensor 152 measures a speed ofthe work vehicle relative to the ground that the work vehicle 10 istraveling on. The ambient sensor 155 measures an ambient air temperatureof the work vehicle 10. The engine speed sensor 160 measures the speedof the engine 55—for example, the revolutions per minute (RPM) of theengine 55. The cooling system sensors 162 measure one or more parametersof a cooling system (not shown) of the work vehicle 10—for examplecoolant temperature, charge air temperature, oil temperature, andrefrigerant pressure. The operator interface 45, the variable pitch fan70, the clutch sensor 150, the ground speed sensor 152, the ambientsensor 155, the engine speed sensor 160, the cooling system sensors 162,and the fan control module 165 may exchange data—for example, parametersand instructions—via a network 166, such as a controller area network.The network 166 may include one or more data buses.

FIG. 4 is functional block diagram of an example implementation of avariable pitch fan control system 400. As shown in FIG. 4, the variablepitch fan control system 400 may include the fan control module 165, theoperator interface 45, the variable pitch fan 70, and a blade pitchdatastore 405. The fan control module 165 may include a blade pitchmodule 402, a reversing module 408, an automatic reversal preventionmodule 411, a manual reversal prevention module 414, a clutch timermodule 418, a max pitch module 422, a max pitch timer module 430, areversal interval timer module 434, a vehicle state module 438, anengine state module 442, and a cooling system state module 450.

In various examples, the fan control module 165 may be a standalonemodule in the work vehicle 10, as illustrated in the example of FIG. 2.In other examples, at least one of the blade pitch module 402, thereversing module 408, the automatic reversal prevention module 411, themanual reversal prevention module 414, the clutch timer module 418, themax pitch module 422, the max pitch timer module 430, the reversalinterval timer module 434, the vehicle state module 438, the enginestate module 442, and the cooling system state module 450 may beimplemented independently or with one or more other modules of the workvehicle 10—for example, an engine control module (ECM), a transmissioncontrol module (TCM), or a powertrain control module (PCM).

With reference to FIGS. 3 and 4, the fan control module 165 controls apitch 135 of a plurality of fan blades 140 of the variable pitch fan 70.The variable pitch fan 70 is driven, either directly or in directly, bythe engine 55 of the work vehicle 10. The variable pitch fan 70 createsan airflow in a first direction 145. The blade pitch module 402 adjuststhe pitch 135 of the plurality of fan blades 140 based on one or moremeasured parameters of a cooling system of the work vehicle 10—forexample, coolant temperature, charge air temperature, ambient airtemperature, and a pressure associated with a heating, ventilation, andair conditioning (HVAC) system of the work vehicle 10. In someimplementations, the blade pitch module 402 receives values of themeasured cooling system parameters from the cooling system sensors 162via the network 166. In other implementations, the blade pitch module402 may receive the measured parameters directly from the cooling systemsensors 162.

The blade pitch module 402 determines the pitch 135 based on at leastone of the measured cooling system parameters and a predetermined targetvalue associated with the parameter. In some implementations, the bladepitch module 402 may include a proportional-integral-derivative (PID)controller that determines the pitch 135 for the variable pitch fan 70.In other implementations, the blade pitch module 402 may use a lookuptable that includes a list of possible parameter values andcorresponding pitch angles.

The reversing module 408 may command the blade pitch module 402 toperform a fan reversal—for example, temporarily cause the pitch 135 ofthe plurality of fan blades 140 to change in order to cause the airflowto flow in a second direction 170, opposite the first direction 145,before causing the airflow to revert back to flowing in the firstdirection 145. The change in airflow direction may remove debris fromthe cooling system, thus, improving the effectiveness of the coolingsystem. The reversing module 408 selectively commands an automatic fanreversal in response to determining that one or more operatingconditions associated with the work vehicle 10 exist. For example, thereversing module 408 may command a fan reversal in response todetermining that the automatic reversal prevention module 411 indicatesthat a fan reversal is permitted and either a clutch of the work vehicle10 has been engaged for at least a first period of time, a measuredcooling system parameter exceeds a threshold, or the variable pitch fan70 is operating at maximum pitch for a second period of time. In someimplementations, the reversing module 408 may generate an alert—forexample, a message displayed on the operator interface 45—in response tonot commanding a fan reversal. The alert may indicate one or moreconditions that prevented the fan reversal.

In some implementations, the reversing module 408 may command a fanreversal in response to the clutch transitioning from engaged todisengaged based on the state of a clutch disengagement reversal statusflag. For example, the reversing module 408 may command an automatic fanreversal in response to the clutch transitioning from engaged todisengaged when the value of the clutch disengagement reversal statusflag is true (enabled). In some implementations, the clutchdisengagement reversal status flag may be set to a predetermined value.In other implementations, the clutch disengagement reversal status flagmay be set to an initial value and the operator of the work vehicle 10may change the value of the clutch disengagement reversal statusflag—for example, via the operator interface 45—to disable or enableautomatic clutch disengagement fan reversals.

The reversing module 408 selectively commands a manual fan reversal inresponse to an operator of the work vehicle 10 requesting a fanreversal. The reversing module 408 commands a manual fan reversal inresponse to receiving an instruction from the operator to reverse thevariable pitch fan 70—for example, via the operator interface 45—anddetermining that the manual reversal prevention module 414 indicatesthat a manual fan reversal is permitted. In some implementations, thereversing module 408 may generate an alert—for example, a messagedisplayed on the operator interface 45—in response to not commanding afan reversal. The alert may indicate one or more conditions thatprevented the fan reversal.

In response to commanding a fan reversal, either automatic or manual,the reversing module 408 may generate an alert to notify the operator ofthe work vehicle 10 that the direction of the air flow associated withthe variable pitch fan 70 is temporarily being reversed. For example,the reversing module 408 may generate and display a message on theoperator interface 45 that indicates a fan reversal is occurring. Thereversing module 408 may also generate an alert notifying the operatorof the work vehicle 10 that fan reversals are not currently permitted.For example, in response to the automatic reversal prevention module 411indicating an automatic fan reversal is not permitted, the reversingmodule 408 may generate and display a message on the operator interface45 that indicates that automatic fan reversals are not currentlypermitted. The generated message may indicate the one or more conditionsthat are currently preventing automatic fan reversals. Similarly, thereversing module 408 may, in response to the manual reversal preventionmodule 414 indicating a manual reversal is not permitted, generate anddisplay a message on the operator interface 45 that indicates manual fanreversals are not currently permitted. The generated message mayindicate the one or more conditions that are currently preventing manualfan reversals.

The clutch timer module 418 generates a first timer value that indicateshow long (i.e., a period) a clutch of the work vehicle 10—for example, aseparator clutch or a cotton fan clutch—has been engaged since thereversing module 408 last commanded a fan reversal. The clutch timermodule 418 increments the first timer when the clutch is engaged. Theclutch timer module 418 resets the first timer when the reversing module408 commands a fan reversal.

The clutch timer module 418 compares the first timer value to a firstperiod (or value) and outputs the results of the comparison to thereversing module 408. In some implementations, the first period is apredetermined period. For example, the first period may be or correspondto approximately 15 minutes. In other implementations, the first periodmay be set to an initial period—for example, 15 minutes—and an operatorof the work vehicle 10, via the operator interface 45, may change thefirst period to another suitable period. Thus, the output of the clutchtimer module 418 indicates whether the clutch has been engaged for atleast the first period since the last commanded fan reversal.

The max pitch module 422 determines an operating state of the variablepitch fan 70 based on the current pitch (e.g., pitch 135) of the blades140 and a measured ambient temperature. The max pitch module 422receives the measured ambient temperature from the ambient sensor 155.The max pitch module 422 uses the blade pitch datastore 405 to determinea maximum blade pitch for the measured ambient temperature. The bladepitch datastore 405 includes a list of possible ambient temperatures.Each listed ambient temperature is associated with a maximum bladepitch. The max pitch module 422 retrieves the maximum blade pitchassociated with the measured ambient temperature from the blade pitchdatastore 405.

In some implementations, the max pitch module 422 provides the retrievedmaximum blade pitch to the blade pitch module 402. The blade pitchmodule 402 may set the pitch 135 of the plurality of fan blades 140 tothe received maximum blade pitch in response to one of the receivedcooling system parameters exceeding a cooling system threshold. Invarious implementations, the blade pitch module 402 may receive one ormore fault codes—for example, diagnostic trouble codes (DTCs)—associatedwith the cooling system. In response to receiving a fault code—forexample, a DTC indicating an open circuit associated with the coolingsystem sensors 162—the blades pitch module 402 may set the pitch 135 ofthe plurality of fan blades 140 to the received maximum blade pitch. Theblade pitch module 402 may not set the pitch 135 to the received maximumblade pitch in response to every received fault code. As an exampleonly, the blade pitch module 402 does not set the pitch 135 to thereceived maximum blade pitch in response to receiving a DTC thatindicates either a blade pitch sensor fault or a hydraulic solenoidvalve driver fault.

The max pitch module 422 receives the current pitch of the blades 140from the blade pitch module 402 and compares the current pitch to theretrieved maximum blade pitch. When the current pitch is greater than orequal to the retrieved maximum blade pitch, the max pitch module 422determines that variable pitch fan 70 is operating at maximum pitch.When the current pitch is less than the retrieved maximum blade pitch,the max pitch module 422 determines that the variable pitch fan 70 isnot operating at maximum pitch. The max pitch module 422 provides thedetermined operating state of the variable pitch fan 70 to the reversingmodule 408 and the max pitch timer module 430.

The max pitch timer module 430 generates a second timer value thatindicates how long (i.e., a period) the variable pitch fan 70 has beencontinuously operating at maximum pitch. The max pitch timer module 430resets the second timer value when the max pitch module 422 indicatesthat the variable pitch fan 70 is not operating at maximum pitch. Themax pitch timer module 430 increments the second timer when the maxpitch module 422 indicates that the variable pitch fan 70 is operatingat maximum pitch.

The max pitch timer module 430 compares the second timer value to asecond predetermined period (or value) and outputs the results of thecomparison to the reversing module 408. For example, the secondpredetermined period may be or correspond to approximately 2 minutes oranother suitable period. Thus, the output of the max pitch timer module430 indicates whether the variable pitch fan 70 has been continuouslyoperating at maximum pitch for at least the second predetermined period.In some implementations, the reversing module 408 may command a fanreversal in response to determining that an automatic fan reversal ispermitted, the variable pitch fan 70 is operating at a maximum pitch,and the measured cooling system parameter is greater than a triggeringthreshold. As an example only, the reversing module 408 may command afan reversal when the automatic reversal prevention module 411 indicatesthat a fan reversal is permitted, the max pitch module 422 indicatesthat the variable pitch fan 70 is operating at maximum pitch, and themeasured coolant temperature is greater than 103 degrees Celsius.

The reversal interval timer module 434 generates a third timer valuethat indicates a length of time (i.e., a period) since the reversingmodule 408 last commanded a fan reversal. The reversal interval timermodule 434 resets and then continuously increments the third timer valuein response to the reversing module 408 commanding a fan reversal. Thereversal interval timer module 434 compares the third timer value to athird predetermined period (or value) and outputs the results of thecomparison to the automatic reversal prevention module 411 and themanual reversal prevention module 414. In some implementations, thethird predetermined period may be or correspond to 120 seconds. In otherimplementations, the third predetermined period may be or correspond to150 seconds or another suitable period. Thus, the output of the reversalinterval timer module 434 indicates whether or not a length of time thatis equal to greater than the third predetermined period has elapsedsince the last commanded fan reversal.

The vehicle state module 438 determines an operating state of the workvehicle 10 based one or more of a ground speed of the work vehicle 10received from the ground speed sensor 152, a status of the clutchreceived from the clutch sensor 150, and a status of a transmission ofthe work vehicle 10. In some implementations, the vehicle state module438 may receive the status of the transmission via the network 166—forexample, from a transmission control module (TCM, not shown). In otherimplementations, the vehicle state module 438 may receive the status ofthe transmission directly from a sensor associated with the transmission(not shown).

The vehicle state module 438 compares the received ground speed to afirst speed threshold. In some implementations, the first speedthreshold may be or correspond to 0.8 kph. In other implementations, thesecond speed threshold may be or correspond to 1 kph or another suitablespeed. In response to the ground speed being less than the first speedthreshold, the vehicle state module 438 determines that the work vehicle10 is operating in a stationary state.

In some implementations, the vehicle state module 438 may compare thereceived ground speed to a second speed threshold. The second speedthreshold may be or correspond to 7 kph. Alternatively, the second speedthreshold may be or correspond to 10 kph or another suitable speed. Inresponse to the ground speed exceeding the second speed threshold andthe clutch sensor 150 indicating that the clutch is disengaged, thevehicle state module 438 determines that the work vehicle 10 isoperating in an estimated road state. In other implementations, thevehicle state module 438 may determine that the work vehicle 10 isoperating in the estimated road state in response to the clutch sensor150 indicating that the clutch is disengaged and the status of thetransmission indicating that both a hydrostatic transmission is not inneutral and that the transmission is in a high gear range.

The vehicle state module 438 provides the determined operating state ofthe work vehicle 10 to the manual reversal prevention module 414. Insome implementations, the vehicle state module 438 may also provide thedetermined operating state of the work vehicle 10 to the automaticreversal prevention module 411.

The engine state module 442 determines an operating state of the engine55 based on a speed of the engine 55 measured by the engine speed sensor160. When the engine speed is less than or equal to a firstpredetermined engine speed, the engine state module 442 determines thatthe engine 55 is in an ultra-low idle state. When the engine speed isgreater than the first predetermined engine speed and less than or equalto a second predetermined engine speed, the engine state module 442determines that the engine is in a below-middle-idle state. When theengine speed is greater than a third predetermined engine speed, theengine state module 442 determines that the engine 55 is in an overspeedstate. As an example only, the first, second, and third predeterminedengine speeds may be 650 revolutions per minute (RPM), 1500 RPM, and2130 RPM, respectively. In other examples, the first, second, and thirdpredetermined engine speeds may be other suitable speeds associated withthe engine 55. The engine state module 442 provides the determinedoperating state of the engine 55 to both the automatic reversalprevention module 411 and the manual reversal prevention module 414.

The cooling system state module 450 may receive one or more faultcodes—for example, diagnostic trouble codes (DTCs)—associated with thecooling system. In some implementations, the cooling system state module450 receives the one or more fault codes via the network 166. In otherimplementations, the cooling system state module 450 may receive a faultcode directly from a component of the cooling system that is generatingthe fault code. In response to receiving at least one fault code, thecooling system state module 450 determines that the cooling system is inan error state. In response to not receiving any faults codes, thecooling system state module 450 determines that the cooling system isoperating in a normal state. The cooling system state module 450provides the determined operating state of the cooling system to theautomatic reversal prevention module 411 and the manual reversalprevention module 414.

The automatic reversal prevention module 411 determines, based on one ormore conditions, whether an automatic fan reversal is permitted andprovides an indication of the determination to the reversing module 408.In response to the reversal interval timer module 434 indicating that alength of time that is greater than or equal to the third predeterminedperiod has not elapsed since the last commanded fan reversal, theautomatic reversal prevention module 411 determines that an automaticfan reversal is not permitted. In response to the engine state module442 indicating that the engine 55 is operating in either the ultra-lowidle state, the below-middle-idle state, or the overspeed state, theautomatic reversal prevention module 411 determines that an automaticfan reversal is not permitted. Performing a fan reversal while theengine is operating in the ultra-low idle state may result in damage tothe variable pitch fan 70 due to decreased oil flow. Performing a fanreversal while the engine 55 is operating in the overspeed state mayresult in a fan hub spring failure.

The automatic reversal prevention module 411 may determine that anautomatic fan reversal is not permitted in response to the vehicle statemodule 438 indicating that the work vehicle 10 is operating in astationary state. In response to receiving an indication from thecooling system state module 450 that the cooling system is operating inan error state, the automatic reversal prevention module 411 determinesthat an automatic fan reversal is not permitted.

The automatic reversal prevention module 411 may permit automaticreversals while the work vehicle 10 is operating in a road or transportmode, either actual or estimated, based on the state of an automaticroad reversal status flag. For example, the automatic reversalprevention module 411 may permit automatic reversals when the value ofthe automatic road reversal status flag is true (enabled) and preventautomatic reversals when the value of the automatic road reversal statusflag is false (disabled). In some implementations, the automatic roadreversal status flag may be set to a predetermined value. In otherimplementations, the automatic road reversal status flag may be set toan initial value and the operator of the work vehicle 10 may change thevalue of the automatic road reversal status flag—for example, via theoperator interface 45—to disable or enable automatic road reversals. Inresponse to determining that the road reversal status flag is false andeither determining that the current mode of the work vehicle 10 is aroad mode or that the vehicle state module 438 indicates that theoperating state of the work vehicle 10 is the estimated road state, theautomatic reversal prevention module 411 determines that an automaticfan reversal is not permitted.

The manual reversal prevention module 414 determines, based on one ormore conditions, whether a manual fan reversal is permitted and providesan indication of the determination to the reversing module 408. Inresponse to the reversal interval timer module 434 indicating that alength of time that is greater than or equal to the third predeterminedperiod has not elapsed since the last commanded fan reversal, the manualreversal prevention module 414 determines that a manual fan reversal isnot permitted. In response to the engine state module 442 indicatingthat the engine 55 is operating in either the ultra-low idle state orthe overspeed state, the manual reversal prevention module 414determines that a manual fan reversal is not permitted.

The manual reversal prevention module 414 may determine that a manualfan reversal is not permitted in response to the vehicle state module438 indicating that the work vehicle 10 is operating in a stationarystate. In response to receiving an indication from the cooling systemstate module 450 that the cooling system is operating in an error state,the manual reversal prevention module 414 determines that a manual fanreversal is not permitted.

The manual reversal prevention module 414 may permit manual reversalswhile the work vehicle 10 is operating in a road or transport mode basedon the state of a manual road reversal status flag. For example, themanual reversal prevention module 414 may permit manual reversals whenthe value of the manual road reversal status flag is true (enabled) andprevent manual reversals when the value of the manual road reversalstatus flag is false (disabled). In some implementations, the, themanual road reversal status flag may be set to a predetermined value. Inother implementations, the manual road reversal status flag may be setto an initial value and the operator of the work vehicle 10 may changethe value of the manual road reversal status flag—for example, via theoperator interface 45—to disable or enable manual road reversals.

The manual reversal prevention module 414 may receive a current mode ofthe work vehicle 10 via the network 166. In response to determining thatthe manual road reversal flag is false and either that the current modeof the work vehicle 10 is a road mode or that the vehicle state module438 indicates that the operating state of the work vehicle 10 is theestimated road state, the manual reversal prevention module 414determines that a manual fan reversal is not permitted.

In various implementations, the automatic reversal prevention module 411and the manual reversal prevention module 414 may receive an indicationof the ambient temperature of the work vehicle 10 from the ambientsensor 155. The automatic reversal prevention module 411 and the manualreversal prevention module 414 each compare the received ambienttemperature to a temperature threshold. In some implementations, thetemperature threshold is a predetermined value—for example, thetemperature threshold may be or correspond to 0 degrees Celsius oranother suitable temperature. In other implementations, the temperaturethreshold may be set to an initial temperature—for example, 0 degreesCelsius—and an operator of the work vehicle 10, via the operatorinterface 45, may change the temperature threshold to another suitabletemperature. In response to the measured ambient temperature being lessthan the temperature threshold, the automatic reversal prevention module411 determines that an automatic fan reversal is not permitted.Similarly, in response to the measured ambient temperature being lessthan the temperature threshold, the manual reversal prevention module414 determines that a manual fan reversal is not permitted.

FIGS. 5A-5C are a flowchart depicting an example method of controllingreversal of a variable pitch fan, such as variable pitch fan 70. In anexample implementation, control may be performed by the fan controlmodule 105. In other implementations, control may be performed by anengine control module (e.g., ECM) or powertrain module (e.g., PCM) ofthe work vehicle 10.

Control begins at 501 of FIG. 5A upon startup of the fan control module165—for example, upon powering on the work vehicle 10. At 501, controlsets the previous sensed state of a clutch of the work vehicle 10(Clutch_Previous) to Disengaged. In additional, control sets a timerthat tracks a length of time the clutch is engaged (Clutch_Timer), atimer that tracks a length of time the variable pitch fan 70continuously operates at maximum pitch (Pitch_Timer), and a timer thattracks a length of time since the last fan reversal (Reversal_Timer) allto zero. Control continues with 504.

At 504, control receives and stores a measurement of a cooling systemparameter (Cooling_Param). For example, the blade pitch module 402 mayreceive a measured coolant or charge air temperature from the coolingsystem sensors 162. Control then determines a fan blade pitch based onthe received cooling system parameter. For example, the blade pitchmodule 402 may determine an appropriate pitch for the blades 140 of thevariable pitch fan 70. Control stores the determined fan blade pitch asa current pitch (Pitch_Current). Control then continues with 507.

At 507, control receives a measured speed of the engine 55 of the workvehicle 10 and determines an operating state of the engine 55—forexample, Ultra_Low_Idle, Below_Mid_Idle, or Over_Speed—based on themeasured engine speed. For example, the engine state module 442 mayreceive the speed of the engine 55 from the engine speed sensor 160.Control stores the determined operating state of the engine(Engine_State). Control continues with 510 where control receives asensed state of the clutch and stores the state as the current state ofthe clutch (Clutch_Current). Control continues with 513.

At 513, control determines whether the clutch is currently engaged—forexample, Clutch_Current is equal to Engaged. If so, control, controlprogresses to 516; otherwise, control transfers to 519. At 516, controlincrements the Clutch_Timer and then control progresses to 522.

At 519, control determines whether the previous sensed state of theclutch was engaged—for example, Clutch_Previous is equal to Engaged. Inother words, control determines whether the clutch has been recentlydisengaged. If so, control progresses to 525; otherwise, controltransfers to 522. At 525, control changes the previously sensed state ofthe clutch to disengaged—for example, control sets Clutch_Previous equalto Disengaged. Control continues with 528.

At 528 control determines whether automatic clutch disengagement fanreversals are enabled. For example, the reversing module 408 checks thevalue of a clutch disengagement reversal status flag. If 528 is true,control progresses to 531 of FIG. 5C, described below; otherwise,control transfers to 522.

At 522 of FIG. 5A, control determines whether the clutch has beenengaged for at least a first period of time since the last fanreversal—for example, Clutch_Timer is greater than or equal to a FirstThreshold. If so, control continues with 531 of FIG. 5C; otherwisecontrol transfers to 537 of FIG. 5B.

At 537 of FIG. 5B, control receives a measured ambient temperature anddetermines a maximum fan blade pitch (Max_Pitch) based on the measuredambient temperature. For example, the max pitch module 422 may receive ameasured ambient temperature of the work vehicle 10 from the ambientsensor 155. Control continues with 543, where control determines whetherthe fan is currently operating at maximum pitch—for example,Pitch_Current is greater than or equal to Max_Pitch. If so, controlprogresses to 546; otherwise, control transfers to 549. At 549, controlrests the timer associated with continuous maximum pitch. For example,control sets Pitch_Timer to zero. Control then progresses to 558 of FIG.5C, described below.

At 546 of FIG. 5B, control increments the timer associated withcontinuous maximum pitch (Pitch_Timer) and then progresses to 552. At552, control determines whether the measured cooling system parameter isgreater than a second threshold—for example, Cooling_Param is greaterthan 103 degrees Celsius. If 552 is true, control transfers to 531 ofFIG. 5C; otherwise, control progresses to 555. At 555, controldetermines whether the fan has been operating at maximum pitch for atleast a second period of time—for example, Pitch_Timer is greater thanor equal to a Third Threshold. If 555 is true, control transfers to 531of FIG. 5C; otherwise, control progresses to 558 of FIG. 5C.

At 531 of FIG. 5C, control determines whether the engine is operating atbelow middle idle—for example, Engine state is equal to Below_Mid_Idle.If so, control transfers to 561; otherwise control progresses to 564.

At 564, control determines whether automatic fan reversals are permittedwhile the work vehicle 10 is in road mode. For example, the automaticreversal prevention module 411 checks the value of an automatic roadreversal status flag. If 564 is true, control continues with 567;otherwise, control transfers to 570. In some implementations, controlmay prevent automatic fan reversals when the work vehicle 10 is ineither a rode mode or an estimated road state and control transfers to588 rather than 570 if 564 is false.

At 567, control determines whether the ambient temperature of the workvehicle 10 is less than a temperature threshold—for example,Ambient_Temp is less than a Fourth Threshold. If 567 is true, controltransfers to 561; otherwise, control progresses to 571. At 571, controldetermines the current state—for example, Normal or Error—of the coolingsystem (Cooling_State). For example, in response to receiving at leastone DTC associated with the cooling system, the cooling system statemodule 450 determines that the cooling system is in an error state. At573, if control determines that current state of the cooling system(Cooling_State) is equal to Error, control transfers to 561; otherwise,control progresses to 576.

At 576, control determines whether at least a third period of time haselapsed since the variable pitch fan 70 was last reversed. For example,control determines whether Reversal_Timer is greater than or equal to aFifth Threshold. If so, control progresses to 579; otherwise, controltransfers to 561. At 579, control determines whether the engine iscurrently operating at either an ultra-low idle or an extremely highspeed—for example, Engine_State is equal to either Ultra_Low_Idle orOver_Speed. If 579 is true, control transfers to 561; otherwise, controlcontinues with 582.

At 582, control adjusts the pitch 135 of the blades of the variablepitch fan 70 to temporality change the direction of the airflow producedby the variable pitch fan 70 from a first direction to a seconddirection. Control resets the timer associated with clutch engagement,the timer associated with the fan continuously operating at maximumpitch, and the timer associated with the last fan reversal—for example,control sets Clutch_Timer, Pitch_Timer, and Reversal_Timer to zero.Control may also generate an alert that indicates that a fan reversalwas commanded. For example, the reversing module 408 may display amessage on the operator interface 45 that states a fan reversal isoccurring. Control then returns to 504 of FIG. 5A.

Returning to 558 of FIG. 5C, control determines whether an operator ofthe work vehicle has requested a fan reversal—in other words, theoperator has performed a manual fan reversal. For example, the reversingmodule 408 determines whether the operator has initiated a fan reversalvia the operator interface 45. If 558 is true, control progresses to585; otherwise, control transfers to 561.

At 585, control determines whether manual fan reversals are permittedwhile the work vehicle 10 is in road mode or an estimated road state.For example, the manual reversal prevention module 414 checks the valueof a manual road reversal status flag. If 585 is true, control continueswith 567; otherwise, control transfers to 588. At 588, control receivesa measured ground speed of the work vehicle and determines a vehiclestate (Vehicle_State) based on the measured ground speed and the sensedstate of the clutch. For example, in response to determining that themeasured ground speed from the ground speed sensor 152 is greater thanor equal to 7 kph and that the clutch is disengaged, the vehicle statemodule 438 determines that the work vehicle 10 is operating in theestimated road state (Road_Est). At 591, control determines whether thevehicle state is an estimated road mode—for example,Vehicle_State=Road_Est. If so, control transfers to 561; otherwisecontrol progresses to 567.

Returning to 561 of FIG. 5C, control determines that a fan reversal,either automatic or manual, was either not initiated or alternativelywas prevented. Accordingly, a fan reversal is not performed, and thetimer associated with fan reversal (Reversal_Timer) is incremented. At561 control may also generate an alert that a fan reversal wasprevented. For example, in response to the operator requesting a manualfan reversal and the manual reversal prevention module 414 determiningthat a manual fan reversal is not permitted, the reversing module 408may display a message on the operator interface 45 regarding theprevented fan reversal. The message may include one or more of theconditions that caused the fan reversal to be prevented—for example, theengine speed is too high. Control then returns to 504 of FIG. 5A.

The foregoing description is merely illustrative in nature and is in noway intended to limit the disclosure, its application, or uses. Thebroad teachings of the disclosure can be implemented in a variety offorms. Therefore, while this disclosure includes particular examples,the true scope of the disclosure should not be so limited since othermodifications will become apparent upon a study of the drawings, thespecification, and the following claims. It should be understood thatone or more steps within a method may be executed in different order (orconcurrently) without altering the principles of the present disclosure.Further, although each of the embodiments is described above as havingcertain features, any one or more of those features described withrespect to any embodiment of the disclosure can be implemented in and/orcombined with features of any of the other embodiments, even if thatcombination is not explicitly described. In other words, the describedembodiments are not mutually exclusive, and permutations of one or moreembodiments with one another remain within the scope of this disclosure.

Spatial and functional relationships between elements (for example,between modules, circuit elements, semiconductor layers, etc.) aredescribed using various terms, including “connected,” “engaged,”“coupled,” “adjacent,” “next to,” “on top of,” “above,” “below,” and“disposed.” Unless explicitly described as being “direct,” when arelationship between first and second elements is described in the abovedisclosure, that relationship can be a direct relationship where noother intervening elements are present between the first and secondelements, but can also be an indirect relationship where one or moreintervening elements are present (either spatially or functionally)between the first and second elements.

As used herein, the phrase at least one of A, B, and C should beconstrued to mean a logical (A OR B OR C), using a non-exclusive logicalOR, and should not be construed to mean “at least one of A, at least oneof B, and at least one of C.” The term subset does not necessarilyrequire a proper subset. In other words, a first subset of a first setmay be coextensive with (equal to) the first set.

In the figures, the direction of an arrow, as indicated by thearrowhead, generally demonstrates the flow of information (such as dataor instructions) that is of interest to the illustration. For example,when element A and element B exchange a variety of information butinformation transmitted from element A to element B is relevant to theillustration, the arrow may point from element A to element B. Thisunidirectional arrow does not imply that no other information istransmitted from element B to element A. Further, for information sentfrom dement A to element B, element B may send requests for, or receiptacknowledgements of, the information to element A.

In this application, including the definitions below, the term “module”or the term “controller” may be replaced with the term “circuit.” Theterm “module” may refer to, be part of, or include: an ApplicationSpecific Integrated Circuit (ASIC), a digital, analog, or mixedanalog/digital discrete circuit; a digital, analog, or mixedanalog/digital integrated circuit, a combinational logic circuit, afield programmable gate array (FPGA); a processor circuit (shared,dedicated, or group) that executes code; a memory circuit (shared,dedicated, or group) that stores code executed by the processor circuit;other suitable hardware components that provide the describedfunctionality; or a combination of some or all of the above, such as ina system-on-chip.

Some or all hardware features of a module may be defined using alanguage for hardware description, such as IEEE Standard 1364-2005(commonly called “Verilog”) and IEEE Standard 1076-2008 (commonly called“VHDL”). The hardware description language may be used to manufactureand/or program a hardware circuit. In some implementations, some or allfeatures of a module may be defined by a language, such as IEEE1666-2005 (commonly called “SystemC”), that encompasses both code, asdescribed below, and hardware description.

The term code, as used above, may include software, firmware, and/ormicrocode, and may refer to programs, routines, functions, classes, datastructures, and/or objects. The term shared processor circuitencompasses a single processor circuit that executes some or all codefrom multiple modules. The term group processor circuit encompasses aprocessor circuit that, in combination with additional processorcircuits, executes some or all code from one or more modules. Referencesto multiple processor circuits encompass multiple processor circuits ondiscrete dies, multiple processor circuits on a single die, multiplecores of a single processor circuit, multiple threads of a singleprocessor circuit, or a combination of the above. The term shared memorycircuit encompasses a single memory circuit that stores some or all codefrom multiple modules. The term group memory circuit encompasses amemory circuit that, in combination with additional memories, storessome or all code from one or more modules.

The term memory circuit is a subset of the term computer-readablemedium. The term computer-readable medium, as used herein, does notencompass transitory electrical or electromagnetic signals propagatingthrough a medium (such as on a carrier wave), the term computer-readablemedium may therefore be considered tangible and non-transitory.Non-limiting examples of a non-transitory computer-readable medium arenonvolatile memory circuits (such as a flash memory circuit, an erasableprogrammable read-only memory circuit, or a mask read-only memorycircuit), volatile memory circuits (such as a static random accessmemory circuit or a dynamic random access memory circuit), magneticstorage media (such as an analog or digital magnetic tape or a hard diskdrive), and optical storage media (such as a CD, a DVD, or a Blu-rayDisc).

The apparatuses and methods described in this application may bepartially or fully implemented by a special purpose computer created byconfiguring a general purpose computer to execute one or more particularfunctions embodied in computer programs. The functional blocks andflowchart elements described above serve as software specifications,which can be translated into the computer programs by the routine workof a skilled technician or programmer.

The computer programs include processor-executable instructions that arestored on at least one non-transitory computer-readable medium. Thecomputer programs may also include or rely on stored data. The computerprograms may encompass a basic input/output system (BIOS) that interactswith hardware of the special purpose computer, device drivers thatinteract with particular devices of the special purpose computer, one ormore operating systems, user applications, background services,background applications, etc.

The computer programs may include: (i) descriptive text to be parsed,such as HTML (hypertext markup language), XML (extensible markuplanguage), or JSON (JavaScript Object Notation), (ii) assembly code,(iii) object code generated from source code by a compiler, (iv) sourcecode for execution by an interpreter, (v) source code for compilationand execution by a just-in-time compiler, etc. As examples only, sourcecode may be written using syntax from languages including C, C++, C#,Objective-C, Swift, Haskell, Go, SQL, R, Lisp, Java®, Fortran, Perl,Pascal, Curl, OCaml, JavaScript®, HTML5 (Hypertext Markup Language 5threvision), Ada, ASP (Active Server Pages), PHP (PHP: HypertextPreprocessor), Scala, Eiffel, Smalltalk, Erlang, Ruby, Flash®, VisualBasic®, Lua, MATLAB, SIMULINK, and Python®.

None of the elements recited in the claims are intended to be ameans-plus-function element within the meaning of 35 U.S.C. § 122(f)unless an element is expressly recited using the phrase “means for,” orin the case of a method claim using the phrases “operation for” or “stepfor.”

What is claimed is:
 1. A fan control system for a variable pitch fan ofa work vehicle, the fan control system comprising: a first sensor thatmeasures a parameter of a cooling system of the work vehicle; a bladepitch module configured to: receive the measured parameter from thefirst sensor, and adjust a pitch of a plurality of blades of thevariable pitch fan based on the measured parameter to generate a firstairflow in a first direction; a reversing module configured toselectively command a fan reversal that includes instructing the bladepitch module to temporarily adjust the pitch of the plurality of bladesof the variable pitch fan to generate a second airflow in a seconddirection; a first timer module configured to: in response to thereversing module commanding the fan reversal, reset and increment afirst timer, and compare the first timer to a first threshold; and afirst reversal prevention module configured to, in response todetermining that the first timer is less than the first threshold,prevent the reversing module from commanding a fan reversal byindicating that a first type of fan reversal is not permitted.
 2. Thefan control system of claim 1 further comprising: a second sensor thatmonitors a status of a clutch of the work vehicle; and a second timermodule configured to: receive the status of the clutch from the secondsensor, in response to the status of the clutch indicating that theclutch is engaged, increment a second timer, and compare the secondtimer to a second threshold, wherein the reversing module is configuredto command a fan reversal in response to determining that (i) the secondtimer is equal to or greater than the second threshold and (ii) thefirst reversal prevention module does not indicate that the first typeof fan reversal is not permitted.
 3. The fan control system of claim 1further comprising a second reversal prevention module configured to, inresponse to determining that the first timer is less than the firstthreshold, prevent the reversing module from commanding the fan reversalby indicating that a second type of fan reversal is not permitted,wherein the reversing module is configured to: receive an instruction,via an operator interface, that requests the second type of fanreversal, and command the fan reversal in response to (i) receiving theinstruction and (ii) determining that the second reversal preventionmodule does not indicate that the second type of fan reversal is notpermitted.
 4. The fan control system of claim 1, wherein the workvehicle includes an engine, the fan control system further comprising: asecond sensor that measures a speed of the engine; and an engine statemodule configured to: receive the measured engine speed from the secondsensor, compare the measured engine speed to a first speed threshold,and compare the measured engine speed to a second speed threshold,wherein: the first reversal prevention module is configured to, inresponse to determining that (i) the measured engine speed is less thanthe first speed threshold or (ii) the measured engine speed is greaterthan the second speed threshold, indicate that the first type of fanreversal is not permitted, and the first speed threshold is less thanthe second speed threshold.
 5. The fan control system of claim 4,wherein the engine state module is configured to compare the measuredengine speed to a third speed threshold, the fan control system furthercomprising: a second reversal prevention module configured to, inresponse to determining that (i) the engine speed is less than the thirdspeed threshold or (ii) the engine speed is greater than the firstthreshold, prevent the reversing module from commanding a fan reversalby indicating that a second type of fan reversal is not permitted,wherein: the reversing module is configured to: receive an instruction,via an operator interface, that requests the second type of fanreversal, and command the fan reversal in response to (i) receiving theinstruction and (ii) determining that the second reversal preventionmodule does not indicate that the second type of fan reversal is notpermitted, and the third speed threshold is less than both the firstspeed threshold and the second speed threshold.
 6. The fan controlsystem of claim 1, further comprising; a third sensor that measures anambient temperature associated with the work vehicle, wherein the firstreversal prevention module is configured to: receive the measuredambient temperature from the third sensor, and in response todetermining that the received ambient temperature is less than atemperature threshold, indicate that the first type of fan reversal isnot permitted.
 7. The fan control system of claim 1 further comprising,a cooling system state module configured to: set a state of the coolingsystem based on at least one code associated with one or more componentsof the cooling system, and in response to receiving at least one faultcode, set the state of the cooling system to an error state, wherein thefirst reversal prevention module is configured to, in response todetermining that the cooling system is in an error state, indicate thatthe first type of fan reversal is not permitted.
 8. A method forcontrolling a variable pitch fan of a work vehicle, the methodcomprising: measuring a parameter of a cooling system of the workvehicle; performing a first fan reversal including temporarily adjustingthe pitch of the plurality of blades of the variable pitch fan togenerate a second airflow in a second direction; resetting andincrementing a first timer in response to performing the fan reversal;comparing the first timer to a first threshold; and preventing a secondfan reversal, in response to determining that the first timer is lessthan the first threshold.
 9. The method of claim 8 further comprising:receiving, from a second sensor, a status of a clutch of the workvehicle; resetting a second timer in response to performing the firstfan reversal; incrementing the second timer in response the status ofthe clutch indicating that the clutch is engaged; comparing the secondtimer to a second threshold; performing a second fan reversal inresponse to determining that the first timer is greater than the firstthreshold and the second timer is greater than the second threshold. 10.The method of claim 8 further comprising performing a second fanreversal in response to (i) receiving a reversal request from anoperator of the work vehicle and (ii) determining that the first timeris greater than the first threshold.
 11. The method of claim 8 whereinthe work vehicle includes an engine, the method comprising: measuring aspeed of the engine; comparing the measured engine speed to a firstspeed threshold, comparing the measured engine speed to a second speedthreshold, and performing a second fan reversal in response todetermining that (i) the first timer is greater than the firstthreshold, (ii) the measured engine speed is greater than the firstspeed threshold, and (iii) the measured engine speed is less than thesecond speed threshold, wherein the first speed threshold is less thanthe second speed threshold.
 12. The method of claim 11 furthercomprising: comparing the measured engine speed to a third speedthreshold; and performing a second fan reversal in response to:receiving a reversal request from an operator of the work vehicle; anddetermining that (i) the first timer is greater than the firstthreshold, (ii) the measured engine speed is greater than the thirdspeed threshold, and (iii) the measured engine speed is less than thesecond speed threshold, wherein the third speed threshold is less thanboth the first speed threshold and the second speed threshold.
 13. Themethod of claim 8 further comprising: receiving, from a third sensor, anambient temperature associated with the work vehicle; comparing thereceived ambient temperature to a temperature threshold; and performinga second fan reversal in response to determining that the first timer isgreater than the first threshold and the received ambient temperature isgreater than the temperature threshold.
 14. The method of claim 9further comprising: determining a cooling state of the cooling systembased on based on at least one code associated with one or morecomponents of the cooling system; and performing a second fan reversalin response to the determining that (i) the first timer is greater thanthe first threshold, (ii) the second timer is greater than the secondthreshold, and (iii) the cooling state is not an error state.
 15. Anon-transitory computer-readable medium storing processor executableinstructions for controlling a variable pitch fan of a work vehicle, theinstructions comprising: measuring a parameter of a cooling system ofthe work vehicle; adjusting a pitch of a plurality of blades of thevariable pitch fan based on the parameter to generate a first airflow ina first direction; performing a first fan reversal including temporarilyadjusting the pitch of the plurality of blades of the variable pitch fanto generate a second airflow in a second direction; resetting andincrementing a first timer in response to performing the first fanreversal; comparing the first timer to a first threshold; and preventinga second fan reversal, in response to determining that the first timeris less than the first threshold.
 16. The non-transitorycomputer-readable medium of claim 15, the instructions furthercomprising: receiving, from a second sensor, a status of a clutch of thework vehicle; resetting a second timer in response to performing thefirst fan reversal; incrementing the second timer in response todetermining that the status of the clutch indicates that the clutch isengaged; comparing the second timer to a second threshold; performing asecond fan reversal in response to determining that the first timer isgreater than the first threshold and the second timer is greater thanthe second threshold.
 17. The non-transitory computer-readable medium ofclaim 15, the instructions further comprising performing a second fanreversal in response to (i) receiving a reversal request from anoperator of the work vehicle and (ii) determining that the first timeris greater than the first threshold.
 18. The non-transitorycomputer-readable medium of claim 15 wherein the work vehicle includesan engine, the instructions further comprising: measuring a speed of theengine; comparing the measured engine speed to a first speed threshold;comparing the measured engine speed to a second speed threshold; andperforming a second fan reversal in response to determining that (i) thefirst timer is greater than the first threshold, (ii) the measuredengine speed is greater than the first speed threshold, and (iii) themeasured engine speed is less than the second speed threshold, whereinthe first speed threshold is less than the second speed threshold. 19.The non-transitory computer-readable medium of claim 18, theinstructions further comprising: comparing the measured engine speed toa third speed threshold; and performing a second fan reversal inresponse to: receiving a reversal request from an operator of the workvehicle; and determining that (i) the first timer is greater than thefirst threshold, (ii) the measured engine speed is greater than thethird speed threshold, and (iii) the measured engine speed is less thanthe second speed threshold, wherein the third speed threshold is lessthan both the first speed threshold and the second speed threshold. 20.The non-transitory computer-readable medium of claim 16, theinstructions further comprising: determining, in response to receivingone or more codes associated with a component of the cooling system, acooling state of the cooling system; and performing a second fanreversal in response to the determining that (i) the first timer isgreater than the first threshold, (ii) the second timer is greater thanthe second threshold, and (iii) the cooling state is not an error state.